Teses / dissertações sobre o tema "Méthode microfluidique"
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Guglielmino, Maud. "Développement d'une nouvelle méthode analytique du formaldéhyde dans l'air basée sur un dispositif microfluidique". Thesis, Strasbourg, 2014. http://www.theses.fr/2014STRAF048.
Texto completo da fonteFormaldehyde (HCHO) is a major pollutant in indoor air. The objective of this work is to realize the scientific and technological advances required to obtain an analytical method based on a microfluidic device to measure air formaldehyde combining precision, selectivity, analysis speed with for major objective a sufficient autonomy on a long time, typically one month. The principle of the method was initially based on three key steps, the gaseous formaldehyde uptake in solution, the formaldehyde derivatization reaction, then the detection of reaction product by colorimetry or fluorimetry. The method has finally advanced toward only two definite steps thanks to the use of an innovative microfluidic device in which uptake and reaction take place simultaneously. The study of analytical performances of the device allows to validate the method developedduring this work
Zhang, Cheng. "Développement d'une méthode microfluidique pour la préparation de microparticules mimes de globules rouges avec une taille et des propriétés mécaniques contrôlables". Thesis, Aix-Marseille, 2020. http://www.theses.fr/2020AIXM0045.
Texto completo da fonteThis thesis focuses on a droplet-based microfluidic method without the addition of surfactants to prepare RBC-like microparticles. The microparticles are obtained by ionic gelation of a natural polymer, sodium alginate (Na-alginate), with calcium chloride to form a gel of calcium alginate (Ca-alginate). Gelation is studied in situ in the microfluidic system or ex situ after the collection of Na-alginate microparticles. The size, the structure and the alginate concentration of the final microparticles are studied according to the operating parameters of the microfluidic system. The microfluidic method developed throughout this thesis allows to control the size and mechanical properties of Ca-alginate microparticles while avoiding their coalescence, despite the absence of surfactants. Thus, monodispersed Ca-alginate microparticles with a Young’s modulus close to that of RBCs are obtained and the feasibility of their use for ultrasonic measurements is also shown. In addition, alternative methods explored in parallel are presented at the end of the thesis
Prigent, Guillaume. "Modélisation et simulation numérique d'écoulements diphasiques pour la microfluidique". Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-01059794.
Texto completo da fonteLac, Etienne. "Déformation et convection d'une capsule dans un écoulement de Stokes tridimensionnel infini". Compiègne, 2003. http://www.theses.fr/2003COMP1461.
Texto completo da fonteBonometti, Thomas. "Développement d'une méthode de simulation d'écoulements à bulles et à gouttes". Toulouse, INPT, 2005. https://hal.science/tel-04582704.
Texto completo da fonteThis work deals with the development of an interface-capturing method aimed at computing three-dimensional incompressible two-phase flows that may involve high density and viscosity ratios and capillary effects. The applications we have in mind concerns chemical engineering as well as environmental problems. We use a front-capturing method to advance the interface but do not perform any explicit reconstruction. We show that the base version of this method results in a smearing of the fronts in regions where the flow undergoes a stray stretching. We propose an improved technique in which the local velocity field within the fronts is modified and the above problem is fixed. This algorithm allows the interfaces to deform properly while maintaining the numerical thickness of the transition region within three computational cells. A detailed study of several aspects of the dynamics of two- and three-phase flows, such as drops in microchannels or hydrodynamic interactions in a bubble swarm, is then performed in both axisymmetric and three-dimensional configurations. The results concerning microfluidics are compared with very recent experiments. Finally, a study of the dynamics of a bubbly suspension involving up to 27 bubbles allow us among other things to enlighten the influence of the bubbles Reynolds number on the velocity fluctuations induced in the liquid
Reyhanian, Mashhadi Mehrnaz. "Simulation numérique par la méthode Monte Carlo (DSMC) et modélisation analytique d'un mélange gazeux dans un micro canal". Paris 6, 2011. http://www.theses.fr/2011PA066396.
Texto completo da fonteAmeur, Djilali. "Modélisation analytique et simulation numérique par la méthode de Monte-Carlo d'un écoulement de gaz dans des micro-canaux". Paris 6, 2008. http://www.theses.fr/2008PA066102.
Texto completo da fonteRua, Gonzalez Diego. "Synthèse de matériaux catalytiques de type oxydes mixtes pour la production de méthanol par la précipitation en flux continu en système microfluidique". Electronic Thesis or Diss., Strasbourg, 2024. http://www.theses.fr/2024STRAF001.
Texto completo da fonteGlobal warming is a concern for the current and future generations due to the increasing greenhouse gases (GHG) emissions to the atmosphere, mainly due to the dependence on fossil fuels. The use of alternative fuels such as sustainable methanol produced from renewable H2 and from CO2 would contribute to reduce the GHG emissions and the effects of climate change. The synthesis of methanol using CO2 rich feedstock is preferentially done by using a solid catalyst composed of CuO, ZnO and ZrO2. This type of catalyst can be produced by coprecipitation of the metal species using a microfluidic device, with advantages that have been demonstrated over catalysts synthesized by batch coprecipitation. In this work, different catalysts for the hydrogenation of CO2 to methanol were synthesized using the microfluidic technique under different conditions, in order to explore different synthesis parameters that could lead to the development of more active catalysts. The differences in the properties and activity between a catalyst synthesized by the microfluidic method and another synthesized by the batch method were investigated, followed by an exploration of the effects of the aging time and the coprecipitation temperature on the catalysts. Lastly, the effect of different compositions of catalysts on the properties and activity were determined, by investigating different CuO contents, the use of CeO2 as a catalyst promoter, and the use of In2O3 as a catalyst promoter and as active metal
Ayed, Ichraf. "Développement d’une méthode de préconcentration de phosphopeptides sur phase monolithique en puce". Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112196/document.
Texto completo da fonteProtein phosphorylation is a key regulator of cellular signaling pathways. It is involved in most cellular events and strictly controls biological processes such as proliferation, differentiation and gene expression. An abnormal phosphorylation can be observed in various diseases such as some cancers or neurodegenerative diseases. Therefore, these proteins are potential biomarkers for the development of diagnostic tools. However, phosphoproteins can be present at low abundance in biological samples and selective enrichment techniques have to be developed prior to the analysis process. One of the most common approaches is based on Immobilized metal affinity chromatography (IMAC). The goal of this work was to develop a microsystem which contains a porous polymer monolith (PPM) as a solid phase extraction for a selective preconcentration of phosphopeptides by IMAC. UV-polymerization and characterization (permeability, porosity and specific area) of a monolith based on ethylene glycol methacrylate phosphate in silica capillaries was first performed. Then, we tried to optimize the different IMAC steps (metal immobilization, sample loading, washing and elution). An efficient immobilization of zirconium on the phosphated PPM was demonstrated by EOF measurements in capillary and confirmed by retention of a model phosphopetide. We demonstrated that the phosphated monolith was also a strong cation exchanger of highly basic peptides. Protocols of loading and elution were also studied but need to be further optimized. Transposition of phosphopeptides enrichment by IMAC on a miniaturized system was then considered. We selected two microchip materials: PDMS is an attractive polymer for its low cost, its ease of microfabrication, its excellent working properties (biocompatibility, UV transparent with low autofluorescence) and many integration possibilities (enrichment, separation and detection) and glass microchip more common and having a good UV transparency. However, PDMS presents two major disadvantages: high absorption property, and oxygen permeability which quench free radical polymerization. Except a few attempts, this material has not been employed successfully as mould for monolith polymerization. To overcome these problems, we investigated several strategies for PDMS surface treatments such as plasma treatment and borosilicate coating. Finally, we demonstrated that our IMAC module performed well on glass microchip. This miniaturized module should be integrated in the future into a microsystem dedicated to the diagnosis of Alzheimer disease
Morthomas, Julien. "Intéractions hydrodynamiques entre colloïdess confinés le long d'une paroi". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13882/document.
Texto completo da fonteApplying a steady electric field or a constant thermal gradient to a colloidal suspension induces a finite velocity of the dispersed particles. The motion of particles is not due to a net body force like in sedimentation but to interfacial forces acting on the electric double layer at their surface. These forces involve a surface flow, which, in turn, results in a velocity field of the surrounding fluid in 1/r³ in the opposite direction of the particle displacement, with r the distance from the centre of the particle. In this work we consider a somewhat different situation, where the suspension is confined to a semi-infinite half space. The particle, under the action of the applied field, is trapped against the solid interface. Still, the creep flow remains; more precisely the particle continues to pump the fluid in the opposite direction. As a consequence there arises a lateral flow along the solid surface towards the particle. Thus others particles inserting themselves in this flow undergo drag forces and form clusters. Particles aggregation has been observed in Electrophoresis deposition and more recently in Thermophoresis deposition for micron sized polystyrene beads in aqueous solution. The total velocity field takes a form significantly more complicated than in the above mentioned unbounded cases; it must satisfy boundary conditions both at the particle surface and at the confining wall. Using the perturbative method of reflections or Oseen method based on Fourier transform we resolve the Stokes equation and find an analytic solution for the drag flow along the interface in powers of the ratio e=a/h of particle radius and wall distance. The usual solution at the zero order induces poor approximation, when following corrections in e involves better results in agreement with experimental measurements of hydrodynamic pair potential between two particles along a wall
Vigneaux, Paul. "Méthodes Level Set pour des problèmes d'interface en microfluidique". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2007. http://tel.archives-ouvertes.fr/tel-00189409.
Texto completo da fonteDans une première partie, nous abordons la problématique du suivi d'interface et présentons en détail les composantes de la méthode Level Set. En particulier, nous détaillons les approches ENO et WENO pour discrétiser les équations de Hamilton-Jacobi ainsi que les diverses méthodes existantes de redistanciation.
Dans la deuxième partie, nous traitons de l'analyse et de la résolution numérique des écoulements bifluides incompressibles pilotés par la tension de surface. Après avoir décrit les modèles mathématiques ainsi que leurs discrétisations et solveurs, nous apportons une contribution nouvelle en dérivant théoriquement une condition de stabilité valable pour les nombres de Reynolds faibles à modérés, caractéristiques des configurations microfluidiques. De plus, on introduit une méthode de décomposition de l'écoulement qui permet de diminuer les temps de simulation.
Enfin, la troisième partie est consacrée à l'application des outils évoqués précédemment pour simuler la dynamique de gouttes dans des microcanaux. Nous présentons les résultats numériques obtenus avec d'une part, un code bidimensionnel cartésien et d'autre part, avec un code tridimensionnel axisymétrique que nous avons entièrement développés. Une bonne adéquation est obtenue relativement aux expériences microfluidiques du laboratoire LOF (Rhodia - CNRS). En particulier, avec nos simulations, nous mettons à jour différentes dynamiques de mélange au sein des gouttes.
Hu, Xu-Qu. "Mouvement et déformation de capsules circulant dans des canaux microfluidiques". Phd thesis, Université de Technologie de Compiègne, 2013. http://tel.archives-ouvertes.fr/tel-00857260.
Texto completo da fonteSarkis, Bruno. "Étude numérique de la relaxation de capsules confinées par couplage des méthodes Volumes Finis - Éléments Finis via la méthode des frontières immergées IBM : influence de l'inertie et du degré de confinement". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS184/document.
Texto completo da fonteCapsules, made of a drop protected by an elastic membrane, are widly present in nature and in diverse industrial applications, but few studies have explored the transient phenomena governing their relaxation. The objective of the PhD is to study the influence of inertia and confinement on the relaxation of a spherical capsule (1) pre-deformed into an ellipsoid and released in a square channel where the fluid is quiescent, (2) flowing in a square channel with a sudden expansion (‘step’). The capsule is modeled as a Newtonian fluid in a hyperelastic membrane without thickness or viscosity and is simulated coupling the Finite Volume - Finite Element - Immersed Boundary Methods. Its relaxation in a quiescent fluid exhibits three phases: the initiation of the fluid motion, the rapid and then slow retraction phases of the membrane. Three regimes exist depending on the confinement ratio and the Reynolds to capillary number ratio: pure, critical or oscillating damping. A Kelvin-Voigt inertial model is proposed to predict the response time constants and also applied to a capsule flowing in the microfluidic channel with a step. The comparison to 3D simulations shows its relevance at short relaxation times. This work paves the way to the study of transient flows of capsules confined in microfluidic devices
Hany, Cindy. "Développement de méthodes thermiques pour la caractérisation de réactions chimiques en microfluidique". Thesis, Bordeaux 1, 2009. http://www.theses.fr/2009BOR13936/document.
Texto completo da fonteThis work deals with the development of new measurement methods in order to characterize high exothermic chemical reactions in safe conditions. Thus, we combine thermal analysis with microfluidic technology. The use of microfluidics allows to manipulate a very small amount of product safely. First, we have developed a microcalorimeter to measure the global heat flux produced in co-flow or droplet-flow configurations. Several parameters can be determined: reaction and mixing enthalpy, concentrations by calorimetric titration and kinetics. The second method uses an InfraRed camera to measure the temperature field of the isoperibolic millireactor. Then, the local evolution of the reaction is estimated by thermal processing. From such inverse methods, the thermokinetic parameters can be determined
Ali, Cherif Anaïs. "Développement de nouvelles méthodes bioanalytiques en microfluidique : de l'immunodosage en goutte au nez artificiel". Paris 6, 2011. http://www.theses.fr/2011PA066435.
Texto completo da fontePaquet-Mercier, François. "Méthodes spectroscopiques et optiques pour le suivi de la croissance des biofilms en milieu microfluidique". Doctoral thesis, Université Laval, 2018. http://hdl.handle.net/20.500.11794/29948.
Texto completo da fonteBiofilms are widely spread among most of earth ecosystems. They can be formed by a variety of microorganisms. In the scope of this thesis, bacterial biofilms, more specifically those formed by the bacterium Pseudomonas sp. CT07, have been studied. They have many roles, useful and harmful, for the human health, agriculture and industry. As opposed to planktonic bacteria that can swim freely, sessile bacteria are attached to surfaces where they can form biofilms. During this process, they produce an extracellular matrix made of, but not exclusively, polysaccharides, proteins, DNA and RNA. The mechanical properties of the matrix make the biofilm very resilient to its surrounding environment. It is viscoelastic, and the bacteria can dynamically modify the mechanical properties of the biofilm. The high variety of functional groups available due to the different biomolecules present allows trapping of organic molecules and dissolved ions by the matrix. This is responsible for multiple mechanism of resistance to antimicrobial by bacteria. The main objective of this thesis is to develop new analytical methodologies to study biofilms and obtain more insights on the structure of biofilms and what can influence them. Infrared spectroscopy and optical microscopy were used in microfluidic channel to follow biofilm growth. The combination of the two techniques enabled acquisition of information on the composition in biomacromolecules and biofilm structure. These methods allowed to assess the efficiency of direct inoculation and inoculation from an upstream biofilm. The use of low aspect ratio channels resulted in strong differences in hydrodynamic conditions between the middle of the channel and the channel corners. In this configuration biofilms tended to grow from the short side-walls of microchannels where shear stress was lowest. Time-lapse confocal microscopy showed the presence of a biochannel inside the biofilm in the corner positions. It is hypothesized that this channel has an important role in mass transfer in biofilm as it grows thicker. As the biofilms of Pseudomonas bacteria grew, their structure could be influenced by the type of growth media. Biofilms grown in complex media obtained from yeast cell extract could form elongated structures called streamers which were analysed with confocal laser scanning microscopy. Three-dimensional imaging of these structures in regular straight microchannels is the first of its kind. In a minimal medium with citrate as the sole carbon source, we observe and quantify time-dependant fractal patterns at the biofilm base. We have also developed a microfluidic device for in situ study by surface enhanced Raman spectroscopy (SERS). This method allows having enhanced Raman signal and high sensitivity of sodium citrate, a common carbon source for bacteria, at low concentration. The different methodology developed in this thesis can be applied to more complex systems in the future. Combination of microfluidic for precise flow control and multiplexed measurement in massively parallelized channels is key to get deeper, statistically relevant insights in biofilm growth and methods to control them.
Cotte, Stéphane. "Développement de technologies de fabrication de microélectrodes sur support microfluidique par des méthodes de lithographie douce". Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00824294.
Texto completo da fonteAutebert, Julien. "Capture and analysis of circulating tumor cells in microfluidics : from conception to clinical validation". Paris 7, 2013. http://www.theses.fr/2013PA077013.
Texto completo da fonteMost cancer deaths are caused by the apparition of metastases, when not treated early enough. By capturing and analyzing the circulating tumor cells (CTC) present in the blood of cancer patient (1 CTC for 10 million white blood cells), it is possible to improve both prognosis and treatment orientatior This manuscript presents the development of a microfluidic device that sorts CTC from blood. The first part presents the context of cancer, and the importance of the detection of CTC in the management of the disease. Existing methods to capture rare cells in microfluidic devices are also studied in detail. The second part presents the development of the device and emphasis the improvements in terms of microfabrication, samples handling and imaging that were achieved during the thesis. The third part presents the results obtained with this device in terns of purity and capture efficiency, not only on model cell lines but also on patient samples. A mathematical model for the capture of the cells is proposed. Finally, the perspectives of this work are presented in the last chapter
Verrier, Nicolas. "Microscopie holographique numérique : modélisation et développement de méthodes pour l'étude des écoulements canalisés et microcanalisés". Phd thesis, Rouen, 2009. http://www.theses.fr/2009ROUES051.
Texto completo da fonteGautam, Bhavesh. "Effets collectifs des micronageurs dans les cristaux liquides nématiques". Electronic Thesis or Diss., Bordeaux, 2024. http://www.theses.fr/2024BORD0062.
Texto completo da fonteThe thesis focuses on the collective effects of microswimmers in nematic liquid crystals. Using lattice Boltzmann simulations, we study a system consisting of spherical swimmers within a nematic liquid crystal. Our findings reveal that coupling between the swimmer flow fields and the liquid crystalline elasticity can destabilize the uniform nematic alignment. In quasi-2D space, we observe the emergence of bend-dominated instability with pushers, which is in agreement with experiments of bacteria in thin nematic films.After opening the 3rd dimension, a spontaneous chiral symmetry breaking is observed; the uniform nematic state becomes unstable and transitions into a cholesteric-like (chiral) state, characterized by a continuous twist in the director field. This is observed for both pusher (extensile) and puller (contractile) swimmers. By analyzing the deformations in the nematic director field, the dominant instability is found to be twist-bend. Our simulations demonstrate that the particle dynamics and nematic director are connected. In the chiral state, both pusher and puller swimmers exhibit helical trajectories.Further, strategies for controlling microswimmer dynamics are also studied. Motivated by bacterial experiments, we consider swimmers of both pusher and puller types within nematic patterns. In agreement with experiments, our findings show that a pusher exhibit circular trajectory in a pure bend and linear trajectory in a pure splay. For a puller swimmer, opposite behavior is observed. Finally, we explore cargo transport of colloidal particles entangled by topological defects. Our simulations suggest that replacing a passive colloid with a spherical swimmer does not affect the shared topological defect and provides motility. The active particle is observed to bind to the cargo via a topological defect. With a pusher swimmer, we observe guided transport along the nematic director, while with a puller, transport is observed to be perpendicular to the nematic director
Barrot, Lattes Christine. "Développement de méthodes expérimentales pour l’analyse des écoulements de liquides dans les microcanaux". Toulouse, INSA, 2007. http://www.theses.fr/2007ISAT0006.
Texto completo da fonteSpecific characteristics of liquid flows in microchannels are investigated. Particularly, three micro-effects which can modify the classical flow-rate versus pressure Poiseuille relationship are identified. The first one is related to the presence of an Electrical Double Layer (EDL) near the channel wall. Based on a critical analysis of the literature, the resulting flow-rate decrease is quantified. An experimental validation requiring local velocities measurements, we have investigated µPIV possibilities and limits in order to obtain a 3-D velocity profile. A method is proposed to improve the resolution in the direction perpendicular to the visualization plane. It has been tested on virtual data and on first real experimental data which need to be completed. In addition, the EDL can also be efficiently used to generate a µflow. We propose an optimisation of a microchannels network intended to fill a micro-vascularized material by electro-osmosis. The second effect is due to viscous dissipation which can modify the fluid properties, mainly the viscosity which is very sensitive to the temperature. An experimental setup for micro-flow rates measurements has been adapted to high pressure levels the effect of temperature rise is clearly highlighted. The experimental data are compared with success to analytical models and numerical simulations. The third effect is tied to the deformation of the walls and is sensitive when they are made in polymer materials. The experimental study and the numerical simulation permit to quantify this deformation and its effects, as a function of the wall thickness
Verrier, Nicolas. "Microscopie holographique numérique : modélisation et développement de méthodes pour l'étude d'écoulements canalisés et microcanalisés". Phd thesis, Université de Rouen, 2009. http://tel.archives-ouvertes.fr/tel-00634672.
Texto completo da fonteLe, Berre Maël. "Dépôt de matière et formation de motifs sur une surface solide : Méthodes microfluidiques, Contrôle par forces capillaires et Génération de vésicules géantes". Phd thesis, Université Pierre et Marie Curie - Paris VI, 2009. http://tel.archives-ouvertes.fr/tel-00388698.
Texto completo da fonteDans la première partie du manuscrit, nous présentons une méthode originale, la micro-aspiration, permettant de réaliser des assemblages réversibles de canaux microfluidiques sur un substrat et servir à guider les liquides. Nous avons étudié les propriétés de ces systèmes avec des modèles physiques simples et appliqué ces phénomènes à la micromanipulation de liquides, le dépôt de protéines à diverses concentrations sur un substrat, la fabrication de motifs de polymères, nanoparticules, gels, etc.
Dans la seconde partie, nous avons exploré des nouvelles méthodes de dépôt de films de phospholipides multicouches sur des substrats solides et les avons appliqués à la fabrication de vésicules unilamellaires géantes de taille contrôlée. Tout d'abord, l'adaptation de techniques conventionnelles (micro-contact printing, moulage, etc.) a permis d'obtenir des motifs de phospholipides de taille micrométrique. Les dépôts ont ensuite été réalisés par retrait d'un ménisque en situation d'évaporation (assemblage capillaire). Nous avons identifié deux régimes de dépôt en fonction de l'importance relative des forces visqueuses et de l'évaporation, permettant un contrôle de l'épaisseur du film jusqu'à 200 nm à la bicouche près. L'émergence d'instabilités de mouillage ou le guidage sur micro-structures ont permis en outre de réaliser des motifs variés. En utilisant des substrats comme électrodes, ces différents niveaux d'organisation ont permis d'obtenir par électroformation des vésicules unilamellaires géantes de taille contrôlée. L'ensemble de ces travaux ouvre de nouvelles voies à la réalisation de surfaces et de motifs micrométriques d'intérêt biologique.
Tahiri, Najim. "Simulation de Globules Rouges modèles, et analyse analytique de modèles de suspensions très concentrées". Phd thesis, Grenoble, 2013. http://tel.archives-ouvertes.fr/tel-01023517.
Texto completo da fonteIcard-Arcizet, Delphine. "Modifications mécaniques et biologiques induites dans des cellules en culture par application locale d'une force contrôlée". Paris 7, 2007. https://tel.archives-ouvertes.fr/tel-00188112.
Texto completo da fonteAdherent cells can control their mechanical properties in order to perform crucial biological functions, like division, migration or differenciation. It has now been proved that cells are very sensitive to the mechanical properties of their substrate, which they sense through integrins. Integrins are transmembrane proteins that link the actin cytoskeleton to the extracellular matrix through scaffolding proteins. We designed an optical tweezers setup controlled by a feedback loop, which allows the application of a constant local force via microbeads bound to the cell integrins. We can thus measure the creep function of a single cell and retrieve an estimate of its rigidity. Simultaneous fluorescence observations allow us to evaluate the impact efforce application on the actin repartition within the cell. We observed that cells stiffen under force application but keep the same rheological response - the creep function still exhibits a power law behavior : J(t) = Atα, in which A decreases on a long time range. Stiffening is coupled to actin recruitment both in the contacts and in the cytoskeleton networtk - up to several um from the force application point. Stiffening and recruitment dynamics seem strongly correlated. This work presents an evaluation of the dynamics of cell Stiffening under stress, which is a novel insight into the elucidation of the more general phenomenon of mechanotransduction
Bisceglia, Émilie. "Méthodes physiques d’extraction de micro-organismes à partir d’échantillons sanguins à l'aide de microsystèmes". Thesis, Cachan, Ecole normale supérieure, 2013. http://www.theses.fr/2013DENS0042/document.
Texto completo da fonteExtraction of pathogens from a biological sample is a key step for efficient diagnostic tests of infectious diseases. For bloodstream infections, current diagnostic methods are usually based on bacterial growth and take several days to provide valuable information. An accelerated result would have a high medical value to adjust therapeutic strategies. The aim of this study is to design a new approach for separation and concentration of microorganisms directly from a blood sample, to avoid time-consuming growth stages. We report a method based on two different microsystems connected in series: it combines modification of conductivity and osmolarity of the sample with generic capture of microorganisms by dielectrophoresis. First we explore the impact of conductivity and osmolarity on the dielectric properties of blood cells and microorganisms. Dilution and acoustic forces are both analyzed to transfer blood cells and microorganisms to the optimized buffer. Then we demonstrate the feasibility of achieving the dielectrophoretic separation of microorganisms from blood cells in a low conductivity and low osmolarity medium inside a fluidic device. The structure of the device is optimized with numerical simulations and experiments performed on blood samples and various microorganisms (E. coli, S. epidermidis and C. albicans).The generic capture of microorganisms is validated, and we achieved a separation of 97% efficiency with E. coli, with an optimal inlet velocity around 100-200 µm.s-1. Finally, we propose an improved microsystem to perform the sample preparation step on a larger volume (1-10mL) in a few hours, in order to fit the medical need
Ollivier-Triquet, Emma. "Dispersion in unsaturated porous media". Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPAST152.
Texto completo da fonteHuman activity has a significant impact on the vadose zone, an area located below the land surface and above the water tables, only partially saturated with water. The vadose is susceptible to pollution from agricultural or industrial activities, posing a threat to water resources. Plus, saturation levels vary greatly, especially with the increasing frequency of droughts due to climate change. Hence, predicting contaminant transport in unsaturated conditions is crucial. However, the understanding of dispersion in unsaturated porous media remains limited, due to the complex interaction of multiphase non-miscible flows with the porous medium. Traditional models such as the Fickian model, described by the Advection-Diffusion Equation, fail to accurately capture dispersion in unsaturated porous media.The objective is to address the issue of transport in unsaturated porous media by identifying relevant properties at the pore scale to understand dispersion at a larger scale. One of the goals is to determine whether dispersion follows Fickian or non-Fickian behavior, as this understanding is crucial for predicting the spreading of pollutant in the vadose zone.To investigate transport in unsaturated porous media, a dual approach is being employed: pore scale transport experiments and Lattice Boltzmann simulations. Direct visualization of fluid structure in natural porous media is challenging. Thus, we use micromodels, transparent interconnected porous networks, to enable optical visualization at the pore scale. First, a micromodel experimental setup was established and optimized to study multiphase flow and transport. Analysis methods were developed, along with techniques for characterizing dispersion through spatial moment analysis.A series of experiments were conducted to obtain initial results on multiphase flow and dispersion. The evolution of saturation and phase distributions with the capillary number was characterized. Transport experiments were performed for the entire range of saturations, showing that dispersion increases as saturation decreases. However, analyzing low saturations was challenging due to the significant increase in dispersion and limitations imposed by the micromodel size, preventing the study of long-term dispersion.To overcome this limitation, Lattice Boltzmann simulations were used for flow and transport, as there is no size limitation except for computational time. However, simulating the distribution of two phases after a multiphase flow in a complex porous medium remains challenging. Generating large-scale images of unsaturated porous media based on experimental data was then crucial for observing late-time dispersion. Machine learning techniques, specifically the Multiple Point Statistic algorithm, were employed to generate images of wider unsaturated porous media and a large dataset of smaller images to increase the statistical significance of the study.Flow and transport simulations were conducted using the generated image dataset to explore the influence of saturation on flow and transport. This involved examining flow properties under saturated and unsaturated conditions. The nature of transport, specifically whether it exhibited Fickian or non-Fickian behavior was investigated. Furthermore, the effect of the Peclet number (a measure of the balance between advection and diffusion) on dispersion for different saturation levels was analyzed.This study revealed that decreasing saturation significantly increases flow heterogeneity, leading to increased dispersion. Notably, the non-Fickian nature of flow tends to be more pronounced with low saturations. Plus, the transition from Fickian to non-Fickian depends on the Peclet number. There is a competition between advection and diffusion in saturated conditions, resulting in a diffusive Fickian regime for low Peclet numbers. However, transport in unsaturated conditions is mainly advective, even at low Peclet, and thus displays a non-Fickian behavior
Garcia, Marine. "Développement d’une plateforme d’imagerie pour la caractérisation du transfert de masse dans les microsystèmes : application aux piles à combustible microfluidiques". Electronic Thesis or Diss., Paris, HESAM, 2024. http://www.theses.fr/2024HESAE007.
Texto completo da fonteFuel cells are devices that convert the energy stored in an oxidant and a reductant into electricity through electrochemical reactions. The most mature technology for this conversion is the proton exchange membrane fuel cell (PEMFC), but other alternative systems are emerging. In particular, microfluidic fuel cells (MFCs) have overcome the problems associated with the use of a membrane and gas storage by using liquid reagents at ambient temperature and pressure. The dimensions of the channel (1-5 mm wide and 20-100 µm high) allow co-laminar flow of the two liquid reagents and the electrolyte in a microchannel containing the electrodes. Therefore, PCMs do not need membrane to separate reactants and performances are driven by charge and mass transport.Experimental characterization of all the physical phenomena involved in PCMs is difficult because actuals methods are more based on electrochemical characterisation. These methods provide an overall characterisation of the system but they do not give precise information on the mass transport phenomena occurring in the channel. To investigate concentration field, numerical modelling is generally used. Numerical methods evaluate the impact of the geometry or the operating conditions on MFC performances. However, the use of these models relies on the knowledge of in-situ parameters such as the diffusion coefficient D and the reaction rate k0. In numerical studies, these parameters are generally approximated leading to a qualitative understanding of the transport phenomena. Furthermore, these numerical studies have not yet been verified by experimental studies.Thus, the main scientific challenge of this thesis is to develop quantitative imaging methods for characterising the concentration field in an operating PCM.To meet this need, an imaging platform based on spectroscopy and three characterisation methods were developed in this thesis. First of all, the work focused on developing an experimental setup based on spectroscopy to study the interdiffusion phenomenon. This study reports the estimation of the diffusion coefficient of potassium permanganate in formic acid. These solutions were specifically chosen because they are used in the PCM developed for the rest of the study.The imaging plateform was then adapted to study the in operando MFC 2D concentration field in steady-state. An analytical mass transfer model (advection/reaction/diffusion) coupled to the 2D concentration field was used to determine the reaction rate. As the concentration variations involved can be very small (few micro-moles), another characterisation technique was implemented to reduce the measurement noise.To improve the signal-to-noise ratio, a method based on modulation of the concentration field was developed. Demodulation of the signal significantly reduced the noise and concentrations of 20 µM were estimated. An analytical model describing the modulated field was established in order to implement an inverse method. The proposed method made it possible to recover the reaction rate associated with the concentration variation.To conclude, the proposed characterisation methods enable the estimation of the mass transfer and the reaction kinetics using the 2D concentration field from an in operando MFC. This technique has been applied to the MFC, but it can be transferred to a micrometric system in which diffusion-advection-reaction phenomena take place
Bisceglia, Émilie. "Méthodes physiques d'extraction de micro-organismes à partir d'échantillons sanguins à l'aide de microsystèmes". Phd thesis, École normale supérieure de Cachan - ENS Cachan, 2013. http://tel.archives-ouvertes.fr/tel-00957785.
Texto completo da fonteGravelle, Simon. "Nanofluidics : a theoretical and numerical investigation of fluid transport in nanochannels". Thesis, Lyon 1, 2015. http://www.theses.fr/2015LYO10238.
Texto completo da fonteThis thesis discusses various situations linked to transport at the nanoscale. The first chapter is an introduction to nanofluidics, containing a review of characteristic lengths, forces, or phenomena existing at the nanoscale. The second chapter is a study of the impact of geometry on the hydrodynamic permeability of a nanopore. This study, inspired by the shape of aquaporins, suggests a possible optimisation of permeability for bi-conical channels. The third chapter is a study of capillary filing inside subnanometric carbon channels which highlights the importance of the disjoining pressure induced by the fluid structuring inside the nanochannel. The fourth chapter is a study of nanofluidic diode, a component known to mimic the behaviour of semiconductor diode. The study highlights a strong coupling between water and ion dynamics which leads to a water flow rectification inside the diode. The fifth and last chapter is a study of the origin of commonly observed pink noise (1=f) in ionic current measurements through nanopores
Blondel, Margaux. "Mécanobiologie des biofilms : influence de facteurs mécaniques sur la prolifération bactérienne par une approche expérimentale in-vitro". Electronic Thesis or Diss., Université de Toulouse (2023-....), 2024. http://www.theses.fr/2024TLSEP023.
Texto completo da fontePostoperative infection is a dreaded complication in human and veterinary orthopedics which can be associated with significant consequences in terms of morbidity, costs and recurrence. Its eradication is difficult, especially due to the development of biofilms on implants used. As a matter of fact, bacteria within a biofilm are tolerant to antibiotics, thus explaining the high number of therapeutic failures when antibiotic therapy alone is used. Investigating factors that could affect biofilm development, and particularly exploring the impacts of the solid and fluid mechanical stresses to which a healing bone is permanently submitted, could allow developing therapeutic strategies alternative to antibiotics and minimize the risk of antibiotic resistances. The main hypothesis of this work consisted in supposing that a mechanical stimulus could modify bacterial proliferation and biofilm formation. The first part of this work is based on describing the clinical aspects of bacterial infection in human and veterinary orthopedic surgery, as well as the mechanisms of biofilm formation. A multiscale approach of the mechanobiology underlying biofilm development is then discussed, starting from the bacterium to reach the biological tissue, and the therapeutic strategies alternative or additional to antibiotics are presented. In the second part, the original experimental workbench developed in this study is presented. A microfluidic device capable of sustaining a bending moment while still allowing bacterial biofilm growth was conceived. It consisted in a chip containing a microchannel molded into PDMS bonded to a flexible PETG coverslip. A mechanical system capable of generating a cyclic bending moment of controlled frequency and amplitude (0 – 2.5 Hz and 0 – 3.10 mm, respectively) was also conceived. The equations governing the kinematical response of the device were provided. The third part of the document presents and discusses the preliminary results of the in vitro study. To quantify biofilm development, PDMS chips were inoculated with a strain of P. aeruginosa containing a fluorescent protein-expressing plasmid. The microfluidic devices thus inoculated were then submitted to a bending moment (dynamic condition), and the static response was used as control. Imaging with epifluorescence microscopy was performed to compare fluorescence in the static chips with that in the dynamic chips. Preliminary results showed that cyclic bending may influence biofilm development. On the one hand, biofilms formed rather randomly along the microchannels submitted to bending, contrary to those formed in the static microchannels during the same period of time. On the other hand, biofilms size and fluorescence intensity were also affected by bending, with intensity remaining unchanged between microscopic images obtained at 24h and at 48h and size increasing. Compared to static results, this latter observation suggests that bending may alter biofilm composition, especially by decreasing bacterial concentration. In conclusion, the methodology presented in this thesis tends towards validating the initial hypothesis regarding the mechanobiological susceptibility of biofilms, in particular under steady state dynamical stimuli. This work suggests a reproducible experimental framework allowing to assess the impact of a dynamic cycle on bacterial biofilm development, and eventually to test therapeutic strategies in a controlled environment
Lugagne, Jean-Baptiste. "Real-time control of a genetic toggle switch". Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC249/document.
Texto completo da fonteRecent progresses in microfluidics, synthetic biology and microscopy automation now make it possible to control gene expression externally and in real time. Among the challenges facing the field of external real-time control of gene expression is the control of intricate, multistable gene regulation networks as well as the control of several target genes at the same time. To advance the domain in this direction we studied the controllability of a simple bistable two-genes network, the so-called genetic toggle switch, in the vicinity of its unstable equilibrium point for extended periods of time. Throughout this document, we present the development of a custom control platform for external control of gene expression at the single-cell level as well as a bacterial cellular chassis and a library of toggle switch genetic circuits for us to control. We use the platform to drive and maintain our genetic system in its region of unstability with both closed-loop and open-loop strategies. Not only do we demonstrate that in silico control platforms can control genetic systems in out-of-equilibrium states, we also notably maintain a population of cells in their unstable area with open-loop periodic stimulations. These results suggest the possible emergence of different regimes of stability in gene regulation networks submitted to fluctuating environments, and can potential insights in the study of cellular decision making. We also introduce a new approach for microscopy image analysis which exploits information hidden in several focal planes around the specimen instead of using only a single-plane image. The objective of this method is to automatically label different parts of an image with machine learning techniques inspired by hyperspectral imaging. The method is then shown to facilitate segmentation and be easily adaptable to various different organisms
Baka, Zakaria. "Élaboration de cancers sur puce pour des applications en thérapies anticancéreuses". Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0175.
Texto completo da fonteOvarian cancer is a major public health issue. Moreover, new treatments still face very high failure rates. This is mainly due to the unreliability of conventional preclinical models such as 2D cell culture. Thus, new tools based on 3D cell culture have emerged such as spheroids and organoids. However, these models have their own limitations (cost, difficulty of application). 3D bioprinting is a new approach to create tunable and reproducible tumor models. However, very few bioprinted tumor models have been reported so far. Besides the “third dimension”, it is important to consider the dynamic conditions of the tumor environment. This has been possible for some years now thanks to microfluidics-based cancer-on-a-chip technology. However, this technology currently does not simulate the drug vascular transport before its interaction with the tumor cells. In this PhD project, we set out to create a dynamic, three-dimensional model of ovarian cancer by combining 3D bioprinting and microfluidics. First, 3D bioprinting was used to create the tumor structure itself. For that, we formulated a bio-ink comprising SKOV-3 ovarian cancer cells and MeWo cancer fibroblasts embedded in a gelatin – alginate hydrogel. The bioprinted tumor structures were then characterized by various techniques to demonstrate their viability and biological relevance. Their response to anticancer drug cisplatin was also assessed. In the second step, we integrated the bioprinted tumor model into a microfluidic support for culture under physiological flow. This support was also intended to simulate the drug's vascular transport prior to interaction with the tumor tissue. We then used computational fluid dynamics to design an improved version of the first system. The aim of this improved version was to simultaneously assess multiple drug concentrations. This PhD project demonstrated the ability of 3D bioprinting to create viable and functional ovarian tumor models. It has also brought interesting research prospects with regard to the possibilities of combining 3D bioprinting and microfluidics to improve preclinical modeling of ovarian tumors
Mutschler, Dimitri. "Étude de l’interaction micro-tourbillon parois chauffées : application aux transferts de chaleur dans les microcanaux". Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1112/document.
Texto completo da fonteThe purpose of this research paper is to determine the role of vortical structures in the improvement of microfluidic cooling systems’ efficiency.This study is presented in two parts. The aim of the first part is to measure heat transfers produced by vortices while interacting with a hot wall. This part was carried out numerically following two steps. The aim of the first step was to improve the understanding of the processes involved during heat transfers in a vortex convected in a laminar flow. As a result, two major processes can be highlighted : the advection of cold particles to the hot wall and an advective mixing. Following these observations, heat transfers produced by a vortical structure were optimized in accordance with its initial characteristics. Consequently, the optimization of heat transfers increased microfluidic cooling systems’ efficiency by more than 50% in the case of vortex streets.The second part combines an experimental study with a numerical model. This study focuses on the creation of vortical structures on a microscopic scale. For this purpose, vortical structures are produced by combination of a synthetic micro jet with a crossflow. The outcome is that several topologies of vortical structures can be observed depending on the Reynolds number of the jet and the crossflow. These topologies can be mapped according to the Reynolds numbers of the system. As a result, a connection can be made between characteristics of some topologies of vortices and control parameters of the system. As a conclusion, the type of structures produced by the cooling system can be controlled
Pham, Thanh Tung. "Multiscale modelling and simulation of slip boundary conditions at fluid-solid interfaces". Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-00980155.
Texto completo da fonteRavey, Christophe. "Estimations de champs de diffusivités, de vitesses et de sources de chaleur par thermographie infrarouge sur des systèmes microfluidiques". Phd thesis, 2011. http://pastel.archives-ouvertes.fr/pastel-00679165.
Texto completo da fonteFortier, Marie-Hélène. "Développement de méthodes analytiques pour la protéomique et l'identification de peptides MHC I issus de cellules leucémiques". Thèse, 2008. http://hdl.handle.net/1866/6563.
Texto completo da fonteRode, García Teresita. "Étude de l’influence de différentes méthodes de fabrication sur l’architecture et les propriétés physico-chimiques des nanoparticules à base de PEG-b-PLA". Thèse, 2017. http://hdl.handle.net/1866/20551.
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